Yes they are trusted, I have been using them for quite sometime and I never had any major issue with them. They are the only licenced company that operate in the freeport, plus they are registered and are regulated by the ministry of law in Singapore.
Your gold is insured and covered by Marsh Insurance. Also your bullion doesn't appear in their balance sheet, so no other party can claim your bullion if the company goes bust, you are the legal owner of the bullion, so you can just go to︀ the freeport and take your precious metals back.